Anthophylite, Mg2Mg5Si8O22(OH)2 is an amphibole mineral, and classed as an asbestos. In this specimen which is a concretion, a grey fibrous aggregate of anthophylite is surrounding a nodule of phlogopite mica. This type of concretion is peculiar to Hefmanov in the Czech republic, and not surprisingly is called a Hefmanov ball.